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Re: [Xen-devel] Questions about the use of idle_vcpu[]

On Mon, 2016-01-18 at 11:07 -0500, Meng Xu wrote:
> On Mon, Jan 18, 2016 at 6:00 AM, Dario Faggioli
> <dario.faggioli@xxxxxxxxxx> wrote:
> > RTDS behavior is broken in many respect, including this,
> > 
> > and in fact,
> > Meng and Tianyang are sending patches already to fix it (I'll let
> > you
> > guys have my comments shortly :-P).
> Right. Tianyang and I are working on changing it from quantum driven
> model to event-driven (or called timer-driven) model. Tianyang sent
> out the first-version patch, but that version has some problems. He
> is
> working on the second version now.
> Hi Dario,
> Tianyang is working on the second version right now.
> If you could have a quick look at our discussion in that thread and
> points out the "serious" issues in the decision, that will be great!
Ok, that's useful to know... I'll do that way.

> We won't repeat the error again and again in the following versions.
> As to the minor issues, we could refine it in the second version.
> (I'm just thinking about how to save your time to have this done. For
> the obvious things that I can handle, I will do it and avoid
> "wasting"
> you time. For the design choices that we are unclear, we definitely
> need your insights/commands. ;-) )
Thanks for all this. :-)

> Hi George,
> Yes, you are right. The current RTDS should not return 0 when the
> idle
> VCPU is picked. I think it should do as what the credit does, i.e.,
> returning a negative value to avoid arming the timer.
> Right now, we are working on changing RTDS to event-driven model. We
> will fix this in theNah, the rework you're doing is big enough, that this 
> change can very well find its place in there.
 next version of the patch.
> If needed, we can send out a separate patch to fix this specific
> issue
> (i.e. it should return negative value when idle vcpu is picked.) I'm
> ok with either way. Which way do you guys prefer?
Nah, the rework you're doing is big enough, that this change can very
well find its place in there.

Doing it right now will need efforts on both our sides, only for the
sake of putting something from "broken" to "just a little bit less
broken" state, and I don't think that's worth. :-P

Thanks and Regards,
<<This happens because I choose it to happen!>> (Raistlin Majere)
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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